1. Field of the Invention
This invention relates generally to fire protection sprinklers of various kinds and relates particularly to sprinkler systems in which a header or branch line is located above a ceiling and is provided with a plurality of drops having adjustable stems which extend downwardly through the ceiling and are provided with sprinklers which automatically operate when the heat within a building caused by fire reaches a predetermined temperature.
2. Description of the Prior Art
In the fire protection industry a sprinkler installation is by definition a means for automatically extinguishing or controlling a fire in its early stages by a system of overhead pipes fitted with devices which operate automatically in case of fire through the action of a heat sensitive feature in its design. The sprinkler installation discharges water under pressure in the form of a spray from one or more sprinkler heads at or near the point of origin of the fire. Ordinarily, an alarm is sounded simultaneously to summon aid to complete the extinction of the fire if necessary and to insure that steps are taken to minimize water damage after the fire is out. When the heat sensitive feature of the system is triggered, water is discharged in all directions below the plane of the sprinkler in a spray pattern which is roughly that of a half sphere substantially filled with water spray. Normally, no water is discharged upwardly to wet the ceiling.
There are many types of sprinkler systems which principally use spray sprinklers for discharge nozzles. Some of these systems include: a wet pipe system in which the piping is normally charged with water under pressure; a dry pipe system in which the piping is normally charged with air under pressure but into which water is automatically admitted when a sprinkler opens; a deluge system in which the pipes normally are empty and open at the heads and the heat sensitive feature is a separate network of heat detectors which control the flow of water; and a preaction system in which there is a separate network of pipes and sealed heads used with pneumatic or electrical detectors that control the introduction of water into the distributive system.
When a sprinkler system is being installed in a building under construction, a plurality of headers or branch lines, which are to be connected to a water main or other source of water under pressure, are installed in generally parallel relationship with each other before the ceiling is constructed. Each of the headers includes a plurality of vertically disposed drops or nipples having pipe threads on at least one end which are connected to the header and such drops normally extend downwardly through an imaginary line which is indicative of the location of the finished ceiling. When the ceiling is being constructed, the plasterboard, acoustic tile or other ceiling material is provided with holes through which the lower ends of the drops project. After the ceiling is substantially completed, the drops are measured, taken out, cut off and threaded, supplied with a desired sprinkler, and are reconnected to the concealed headers or branch lines. This has been difficult since it usually requires that the workman have access to the area above the ceiling so that the pipe threads at the upper ends of the drops may be tightened.
Normally ceilings may be either fixed or floating. In a fixed ceiling the ceiling material is connected directly to rafters or other structure between floors of a building, and in a floating ceiling the ceiling material is usually mounted on a framework or grid which is suspended from the rafters with a space between the ceiling material and the rafters. Frequently a floating ceiling is constructed of acoustical tile or the like which can be removed to provide access to the space above the ceiling, but fixed ceilings have been especially difficult since the drops must be fitted using trial and error methods based on an estimated location of the finished ceiling.
In the past some efforts have been made to reduce the amount of labor involved which is required in removing and changing the length of the sprinkler drops and these efforts have included adjustable sprinkler drops which are threaded on the end to receive a sprinkler and are telescopically mounted on the header. However, these prior art devices have been used primarily with floating ceilings since some access must be had above the ceiling after the ceiling is constructed so that the adjustment can be made in order for the sprinkler head at the lower end to be substantially flush with the ceiling.
Some examples of prior art adjustable stem sprinkler drops for overhead fire protection sprinkler systems are the U.S. Pat. Nos. to Faulkner et al 3,194,316; Adams, Jr. 3,529,671; and Horwinski 3,847,392.
These prior art structures generally have not been entirely satisfactory since insurance companies and fire underwriters normally require that water under a pressure of at least 100 pounds per square inch be used in the sprinkler system and the industry standards require that the system be tested at between 200 and 250 pounds per square inch water pressure. Prior art structures which have utilized O-rings as a seal usually do not stand up under pressures in excess of 150 pounds per square inch without leaking while the prior art structures which included a compression gasket suffered from the possibility of a blow-out in which the entire adjustable stem including the sprinkler was forced out of the pipe by the water pressure.